Generally, a rotary joint refers to a mechanism which can join a fixed portion and rotating portion of a machine and circulate a fluid between the fixed portion and rotating portion without leakage.
A gap is provided in a sliding-contact portion between the fixed portion and rotating portion of the machine to join the fixed portion and rotating portion and circulate a fluid between the fixed portion and rotating portion without leakage, and the gap needs to be sealed to prevent the fluid from leaking.
Conventional rotary joints are configured to be able to receive and deliver the fluid, with the fixed portion provided on an outer circumferential section, the rotating portion installed as a rotating shaft in the fixed portion, a fluid flow path installed in the rotating shaft, an inlet and outlet of the fluid flow path installed in a circumferential surface of the fluid flow path, and an annular groove installed in an inside part of the rotating portion corresponding to a rotation trajectory of the inlet and outlet of the fluid flow path. A sealing member is installed between the fixed portion and rotating portion around the fluid flow path to prevent leakage of the fluid (Japanese Patent Laid-Open No. 2006-95616).
Since the cryo-rotary joint uses a refrigerant as a fluid, it is preferable to thermally insulate the refrigerant using a vacuum, but introduction of a vacuum portion tends to increase apparatus size in radial direction. Also, functions of the sealing member, which is placed in contact with the refrigerant, is impaired by freezing. Also, there will be leakage of the fluid. Also, a joint portion will grow in size even if not frozen. Furthermore, frictional heat of the sealing member is transmitted to the refrigerant, increasing temperature of the refrigerant and posing an additional problem in that the refrigerant needs to be supplied in large amounts.
FIG. 10 shows a conventional cryo-rotary joint.
The cryo-rotary joint 101 in FIG. 10 is fixed to an end wall on a side opposite to an output shaft 103 of a rotating machine 102 and configured to be able to supply a refrigerant to a target part 104 of the rotating machine 102.
A rotating portion is shown shaded in FIG. 10. The rotating portion of the cryo-rotary joint 101 makes up a rotating shaft 105 rotatably supported in a housing 106 of a fixed portion.
A refrigerant supply tube 107 and refrigerant return tube 108 are installed in the rotating shaft 105 in such a way as to be rotatable with the rotating shaft 105.
The rest of the rotating shaft 105 except for the refrigerant supply tube 107 and refrigerant return tube 108 makes up a vacuum chamber to thermally insulate the refrigerant supply tube 107 and refrigerant return tube 108 using a vacuum.
Disk-shaped rotating-side members 109 and 110 are installed on a circumferential surface of the rotating shaft 105, allowing passage of the refrigerant supply tube 107 and refrigerant return tube 108 therethrough and serving as a rotating side of a relatively rotating member.
An evacuation hole 111 for use to evacuate the interior of the rotating shaft 105 is provided in an end wall of the rotating shaft 105.
Refrigerant chambers 112 and 113 adapted to receive outlets of the refrigerant supply tube 107 and refrigerant return tube 108 are installed inside the housing 106. A disk-shaped partition wall 114 is installed between the refrigerant chambers 112 and 113, partitioning the refrigerant chambers 112 and 113 from each other and getting between the disk-shaped rotating-side members 109 and 110.
Refrigerant supply channel 115 and refrigerant return channel 116 are installed in the housing 106, being communicated with the refrigerant chambers 112 and 113, respectively. Also, an evacuated channel 117 communicated with the evacuation hole 111 is installed in the housing 106.
The refrigerant supply tube 107 and refrigerant supply channel 115 form a flow path for supply of the refrigerant. On the other hand, the refrigerant return tube 108 and refrigerant return channel 116 form a flow path for return of the refrigerant. The evacuation hole 111 and evacuated channel 117 form a flow path for evacuation.
A bellows 118 and sealing member 119 are respectively installed between each of both sides of the disk-shaped rotating-side member 109 and an inner wall of the refrigerant chamber 112, and the disk-shaped partition wall 114.
The bellows 118 resiliently presses the sealing member 119 against the disk-shaped rotating-side member 109.
Consequently, in the flow path for supply of the refrigerant, the refrigerant delivered from the housing's refrigerant supply channel 115 on the stationary side to the refrigerant supply tube 107 on the rotating side is prevented from leaking from the refrigerant chamber 112 serving as a supply location.
Reference numeral 120 denotes sealing members adapted to seal connections with an external refrigerant tube.
Similarly, a bellows 118 and sealing member 119 are respectively installed between each of both sides of the disk-shaped rotating-side member 110 and an inner wall of the refrigerant chamber 113, and the disk-shaped partition wall 114.
In the flow path for return of the refrigerant, the bellows 118 and sealing member 119 prevent the refrigerant delivered from the refrigerant return tube 108 on the rotating side to the housing's refrigerant return channel 116 on the stationary side from leaking from the refrigerant chamber 113 serving as a supply location.